A woven plastic bag has a layer of woven-together plastic strips that are mostly exposed on an inner surface of the bag in sections and partly covered with coatings of plastic.
Specifically, the invention relates to a method of making a woven plastic bag as described in DE 10 2011 080 462 where                a flat-lying fabric web is fed along a production direction and has on a first top side an exposed layer of woven-together plastic strips, the fabric web extending perpendicular to the production direction along a transverse direction and each extending over 10% of the width of the fabric web and, between them, a middle section, the fabric web being provided with a pattern that repeats in the production direction on the first face of the fabric web of local coatings in the form of a film or of a liquid plastic,        the fabric web is reshaped into a fabric tube, and        the fabric web, in order to form individual woven plastic bags, is separated into pieces of the fabric tube that are subsequently filled and sealed.        
Woven plastic bags are characterized by good functional characteristics, particularly by a high load capacity. In general, the woven-together plastic strips are connected to a polymer film that forms the outer surface of the woven plastic bag. The polymer film of the outer surface gives the bag a high-quality appearance and seal the bag wall. Moreover, the individual strips of the fabric are fixed to one another, thus stabilizing the weave. The fabric is preferably made of polypropylene.
The fabric and the polymer film forming the outer surface are bonded flatly to each other and form a strong woven plastic laminate. The polymer film can be a separate film and laminated with the fabric or can even be extruded onto the fabric.
In principle, it is possible to also provide a coating, for example in the form of a film, at zones on the inner face of the bag, in which case the material and manufacturing costs rise substantially, however.
If the fabric on the inside of the bag is not provided with a coating, the woven plastic bag is usually sealed together by adhesive strips, because the woven-together plastic strips cannot be reliably and tightly thermal welded.
In order to also enable closing of a woven plastic bag by thermal welds without providing the entire fabric with a coating, a coating is applied only in the form of strips that run transversely on the fabric web when it is lying flat. The strips extend with a constant strip width—i.e., a constant length in the production direction—over nearly the entire width, with the coating either being omitted in the outer edge regions or transitioning into a coating running in the production direction in the manner of a strip.
As a result of the coating running in the transverse direction, a thermal weld can be produced in order to easily seal the woven plastic bag. This offers the advantage that the coating is applied only in places in which a sealing is to be formed, thus resulting in substantial savings in materials. Like with a woven plastic bag that is provided over the entire inside with a coating and sealed, they must generally be opened with scissors, since it is difficult to tear the woven-together plastic strips.